Hey Guys,

I thought I would forward a post from the Lancair ES list concerning rotaries (oldest post on the bottom).  There are very few rotary powered Lancairs, so I’m kinda the front man on this one by default.  I may come to some of the Fly Rotary “experts” for help if I get in a corner, but so far, everyone’s been polite and its been a fun exchange. 

 

I’m sure there is more to come. 

 

Mark Steitle

Lancair ES – N/A 20B

 

 

 

Gary,

First, it is not my intent to flame you or anyone else.  I only strive to educate.  I don’t know just where your calculations are off, but obviously something is amiss.  Mazda rated the N/A 13B 2-rotor engines anywhere from 160 to 180 hp.  The 2.0L 3-rotor was only produced in a turbo model (20B-REW) and was rated at a very conservative 299hp.  The new RX-8 Renesis engine (a 1.3L n/a 2-rotor) is rated at 238 hp. 

 

Attached is a hp/torque chart from the Mazda 26B 4-rotor engine that was used in the Mazda LeMans race car, and won the LeMans in 1990.  It shows that it produced 675hp at 9000rpm.  That is over 150 hp/rotor.  While this engine was a peripheral-ported engine, it also was normally-aspirated.  Mazdatrix recently dyno’d a N/A peripheral-ported 13B for Paul Lamar at 250hp @ 6000rpm, running a carburetor.  That is an easy 125hp/rotor, and 250 hp from a 195# engine.  (While 6000rpm might sound high, keep in mind that the crank turns 3X the rotor speed.  So, when the crank is turning 6000rpm, the rotors are only going 2000rpm.)

 

Also attached is a dyno chart by Atkins Rotary showing a turbo 3-rotor producing 375hp at 6200.  This is in the rpm ballpark of where you would normally operate a rotary airplane engine running a 2.85:1 gearbox, such as the RWS model RD2-C.  It should be noted that the rotary’s lowest bearing loads occur at 5900 rpm.  So, 6200 is very close to the “sweet spot” as far as bearing loads are concerned.

 

Turbo’d rotaries can produce an incredible amount of power for their size.  500hp from a turbo-charged 13B in not all that unusual.  That would correlate to 750hp from a 3-rotor at the same boost.  So, 580hp at 7000 is well within reach of the common man.  A Velocity builder in California (Al Glitzen) recently dyno’d his N/A 20B at 275 hp @ 6000.   

 

In the early days of the rotary, they were beating the pants off of all the competition, so the SCCA came up with an equalizer formula to make racing fair for all participants.  It effectively doubles the 1.3L displacement and treats it is a 2.6L.  If you compare the airflow of the 1.3L rotary engine it pumps as much air as a 2.6L 4-stroke piston engine would.  So, the SCCA considers the displacement to be 2.6L for the 13B and 3.9L for the 20B.  Maybe this helps explain why they produce more hp than your calculations would indicate.

 

As you pointed out, one of the most attractive features of the rotary is its soft failure modes.  If they’re running when the failure occurs, they will usually keep running until they are shut down, then they will refuse to re-start.  The 13B has only 3 moving parts, two pistons and a crank.  Pistons are cast iron and the crank is bullet-proof. 

 

For more information, check out the ACRE (AirCraft Rotary Engine) web site at www.rotaryeng.net.  

 

Mark Steitle 

 

 

 

 

 

I should probably take this to the rotary engine list as they seem to 
have napalm ready to flame us "disbelievers", but here goes:  A 
naturally aspirated 2-liter Mazda engine, according to my 
predictions, would produce about 160 hp at 7,000 rpm.  Under boost, 
and I don't know whether this one is running 39 inches (Hg?) manifold 
pressure or more likely 10 psi boost, which would be about 50 inches 
Hg, I would predict a power output of 275, maybe a little less.  This 
roughly correlates to 275 hp for the last twin-turbo RX7, which ran 
to about 8500 rpm.  The claim below is 580 hp, or twice my prediction 
and about twice the best specific output from Mazda.  And then the 
580 hp at 7,000 would be equivalent to a torque of 435 ft-lb, which 
is higher than the peak torque stated (386 ft-lb).

All that is not to say it wouldn't make a good engine for the ES.  It 
would tolerate 50 inches of manifold pressure and 7,000 rpm quite 
well and that would produce 275 hp.  With some effort the turbo setup 
could be matched to give a critical altitude of 10,000 ft.  Power 
would probably fall off to maybe 200 hp at 20,000 ft, still 
respectable.  The thing that always bothered my about the rotary 
option is the relatively high fuel consumption, maybe 10% higher than 
a piston engine.   The thing that is attractive is that there are 
very few catastrophic failure modes.  They will keep running with a 
broken apex seal and even with no coolant.

Gary Casey
On Mar 21, 2006, at 9:30 AM, <fpbjr2001@yahoo.com> wrote:

> ed
>   the rotary is a 20b. a 2 liter or 120 cu. in.
> engine.
> we have an IVO prop on it to get us through the 40hr
> test. we are going to look at the MT prop at sun-n-fun
> and we have a prop that chuck diaz has designed for
> the rotary community. we are going to ground test it
> before another guy flight test it.
>       paul brannon  N117ES
>
> --- erosiak@comcast.net wrote:
>
>> Paul,
>>
>> What is the cubic inch engine size of the rotary,
>> and what prop will you use??
>>
>> Ed Rosiak
>>
>>
>>  -------------- Original message
>> ----------------------
>> From: <fpbjr2001@yahoo.com>
>>
>>
>>
>>> From:    <fpbjr2001@yahoo.com>
>> To:    Lancair_ES@yahoogroups.com
>> Subject:    RE: [Lancair_ES] Someone talk some sense
>> into me!
>> Date:    Tue, 21 Mar 2006 15:22:13 +0000
>>
>
> ---------------------------------
> bryan
>   no! no! we hope to be a little better than piston
> speeds.
>   we did dyno the engine. 39" mp (10 lbs boost) it
> made 580 hp @7000rpm and 386ft/lb torgue @ 5400 rpm.
>  we will turbo normalize with 3 lbs boost or 33" mp
> and make about 330-350 hp.
>            paul brannon   N117ES
>
> --- bjburr@mwheli.com wrote:




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